This invention relates to improved nutritionally useful, amino acid food additives, the method of making them and the fortification of foodstuffs which are deficient in the nutritionally related amino acids. The term "amino acid material" is meant to encompass nutritionally useful amino acid compounds per se, whether they are in the form of amino acid derivatives, their esters, salts or mixtures thereof. The term "proteinaceous foodstuff" is meant to encompass protein per se, whether derived from vegetable or animal sources, and additionally, to manufactured products intended for human or animal consumption containing such proteins as a significant component.
There is considerable impetus to satisfy the protein requirement in the diet of man with protein derived exclusively from vegetable sources. There are essentially two reasons which compel human populations to look to vegetable proteins for a substantial, if not an exclusive, source of dietary protein. The paramount reason is one of efficiency. That is, at least in certain parts of the world, it is no longer feasible, from the standpoint of consumption of energy, to grow a crop, to feed livestock, to obtain required dietary protein. The second reason is best couched in terms of nutrition and health. Manufactured foodstuffs based on vegetable proteins afford the possibility of ultimately achieving a perfect balance of nutrients with controlled exclusion of certain identified detrimental agents, such as cholesterol. And, there are subsidiary reasons involving the factor of convenience, and, to some, reasons of personal conviction.
There appears to be no question as to the capacity to obtain vegetable proteins in sufficient quantity. Success in the agriculture of, for example, the legumes (and in particular soy and peanut) have assured the ready procurement of vegetable protein in quantity. And this assurance of quantity is, in part, attributable to the development of associated technologies to exploit and make available this source of native vegetable protein. George Washington Carver, e.g., is famous for his pioneer work in developing numerous ways of preparing and growing the peanut and other vegetable protein for human consumption.
Now the principal concern is one of quality of that vegetable protein. If the vegetable protein is not nutritionally the equivalent of protein derived from animal sources, that is, of comparable quality, the fact that the vegetable protein is obtainable in quantity is of lessened significance. The fact is that proteins derived from a chosen plant species source are not of comparable nutritional quality to animal sources. This is evident, in part, by examination of the amino acid content, or profile, of a chosen plant protein. For example, peanut protein is deficient in the sulfur-containing amino acids, such as methionine; wheat gluten is deficient in lysine. Nutritionists have applied the term "limiting" to such amino acids, and have noticed that a protein characterized by a particular limiting essential amino acid is effectively levelled in nutritive value to the content of the first limiting amino acid. For example, if a certain vegetable protein was relied upon for the sole source of dietary protein, and if that protein was characterized by an amino acid profile revealing certain limiting amino acids, it would be necessary to consume in the diet an excessive amount of that protein in order to insure the nutritionally required intake of those limiting essential amino acids. Besides the sheer economic waste of such a diet, there is increasing evidence in the scientific literature that excess dietary protein may have detrimental physiological effects.
Fortification of proteinaceous foodstuffs with, e.g., sulfur-containing amino acids, and particularly with respect to methionine, has typically involved direct addition of DL-methionine as the free acid. However, all attempts to fortify methionine deficient foodstuffs with free DL-methionine proved unfeasible because of a severely intractable flavor problem. It was discovered that foodstuffs so fortified with DL-methionine developed off-flavors and became discolored. This effect was particularly noticeable for foodstuffs that were either heated prior to eating, or were stored for an indefinite period in a hydrated condition, but the effect was also noticed after dry storage. The chemical basis for the generation of these off-flavors and unsightly discolorations was, in part, attributable to the well-known Strecker degradation--or more commonly, the Maillard reaction (chemical browning). The Maillard reaction is particularly distressing when sulfur-containing amino acids are involved because of the generation and liberation of noxious mercaptans and sulfides, e.g. methional is freely formed in foodstuffs fortified with methionine. Also, distinct from the Maillard reaction, degradative reactions, such as air oxidation of these sulfur-containing amino acids, adversely affect flavor. Needless to say, alternate means were sought to alleviate the sulfur amino acid deficiencies in vegetable derived proteins.
Some prior art methods are designed to defeat the Maillard reaction in the face of free addition of selected amino acids. Representative diverse means suggested by the prior art are: (1) encapsulation of the free amino acid; (2) simultaneous incorporation of certain alleged anti-browning agents, e.g. pyrocarbonic acid esters, and O-carboxy anhydrides of .alpha.-anhydroxy acids (U.S. Pat. No. 3,337,348 granted Aug. 22, 1967); and (3) utilization of the plastein reaction. This last-mentioned means involves the bonding of the added amino acid by peptide linkage to protein molecules which constitute the bulk of the proteinaceous component of the foodstuff. All of the above-listed means are of limited practical utility. Consequently, the prior art continued the search for means in circumvention of the Maillard reaction. Among these means were suggested the utilization of tasteless derivatives of certain amino acids which were relatively inert to degradation yet nutritionally available on ingestion.
For example, some success has been achieved in derivatization of certain sulfur-containing amino acids, especially methionine. For example, Ralph Anthony Damico and Robert Wayne Boggs in U.S. Pat. No. 3,878,305, Apr. 15, 1975, discloses that certain N-acyl L-methionine compounds, exhibit increased stability, attenuated taste characteristics and are nutritionally available. Damico and Boggs in U.S. Pat. No. 3,952,115 achieved additional successes on ester derivations of N-acyl L-methionine. The teachings of U.S. Pat. Nos. 3,878,305 and 3,952,115 are incorporated herein in their entirety.
While the above amino acid derivatives solved some of the aforementioned problems, direct addition of some amino acid derivatives still causes undesirable flavors in certain foodstuffs. In some cases, they have proven to be unstable in some food systems. The addition of NALM, e.g. peanut butter, results in unwanted appearance, flavor and textural changes upon storage conditions.
It is an object of the present invention to reduce or eliminate the undesirable off-flavors of free amino acid food additives.
Another object is to provide a method of dehydrating an aqueous solution of amino acids, their salts and derivatives using conventional drying techniques to provide an amino acid containing powder having a lower hygroscopicity.
Still another object of the present invention is to provide an improved-tasting amino acid fortified proteinaceous foodstuff, particularly peanut butter.
These and other objects will become apparent in the light of this disclosure.